Control system for cutting apparatus



Oct. 20, 1953 VANDENBERG 2,655,994

CONTROL SYSTEM FOR CUTTING APPARATUS Filed May 31, 1950 2 Sheets-Sheet l Ac'ruming Mechanism WITNESSES: Q INVENTOR f Frank Vondenberg,

90M g 2 4 Q QM Y Oct. 20, 1953 F. VANDENBERG 2,655,994

CONTROL SYSTEM FOR CUTTING APPARATUS Filed May 31, 1950 2 Sheets-Sheet 2 WITNESSES: ,0 2 INVENTOR g; I I I [2 Frank Vondenb.

E Qty/ fl/ill l/ b d] Fig.3. ATTNEY Patented Oct. 20, 1953 CONTROL SYSTEM FOR CUTTING APPARATUS Frank Vandenberg, East Aurora, N. Y., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application May 31, 1950, Serial No. 165,207

9 Claims.

Generally stated, it is an object of my invention to provide a control system for cutting apparatus which is simple and inexpensive to manufacture, and is reliable and accurate in operation.

More specifically, it is an object of my invention to provide, in a control system for a shear, for utilizing spaced impulses disposed in accordance with the speed of a strip of moving material for determining the starting time of a shear for cutting predetermined lengths from the strip.

Another object of my invention is to provide, in a shear control system, for utilizing a delayed impulse to initiate operation of a shear and for utilizing a fixed reference voltage in conjunction with a position-responsive synchrovoltage and a speed reference voltage for controlling the operation of the shear and returning it accurately to a rest position.

Yet another object of my invention is to provide, in a control system for a shear, for utilizing a timer voltage produced in accordance with the speed of a strip of material for accelerating a shear and subsequently removing the timer voltage and utilizing a synchronous control voltage responsive to the position of the shear and a fixed reference voltage for stopping the shear and maintaining it in a rest position.

It is also an object of my invention to provide, in a control system for a shear, for utilizing an electronic regulator, which is responsive to the algebraic sum of a timer voltage, a synchronous position-responsive voltage and opposed speed responsive and reference voltages, for accelerating and subsequently stopping a shear motor.

Other objects will in part be obvious, and will in part be explained hereinafter.

In practicing my invention according to one of its embodiments, timed impulses are produced as end of a strip of material, which is to be cut, passes spaced apart photoelectric devices adjustably disposed on the cut-off side of the shear. These impulses are applied to a timer which produces a starting impulse which is delayed in accordance with the speed of the strip, and is applied to a regulator for the driving motor of a shear in conjunction with a fixed reference voltage, a variable shear position-responsive voltage and a speed-responsive voltage. The regulator rapidly builds up the voltage applied to the shear motor until limit switches actuated by the shear interrupt the connection of the timer to the regulator after slightly more than one-half revolution of the shear and also disconnect the photoelectric devices from the timer. The regulator then operates under the influence of the position responsive voltage, the reference voltage, and the speed responsive voltage to reduce the voltage applied to the shear motor and bring it to an accurate stop. The limit switches reclose as the shear approaches its rest position so as to reset the control for the next cutting operation.

For a more complete understanding of the nature and scope of my invention, reference may be made to the following detailed description which may be read in connection with the accompanying drawings, in which:

Figures 1 and 2, positioned one above the other, represent diagrammatically a shear control system embodying the invention in one of its forms; and

Fig. 3 illustrates curves representing the voltages applied to the regulator for controlling the shear through an operating cycle.

Referring to the system of Figs. 1 and 2, the reference numeral [2 may denote, generally, a shear of the up-cut type, comprising a stationary upper blade l3 and a movable lower blade [4 which may be actuated through a suitable mechanism I5 by means of a shear motor I! for cutting a moving strip of material I9. A conveyor belt 20 may be provided for removing sheets out from the strip Hi, the speed of the conveyor belt being preferably about 20% greater than the speed of the strip 19 so as to ensure removing sheared sheets as expeditiously as possible.

The shear motor I! may comprise an armature Ila and a field winding llb. The field winding l'lb may be supplied with electrical energy from a suitable source of substantially constant potential, While the armature l'la may be supplied with electrical energy from a main generator 22 comprising an armature 22a, a main field winding 22!) and a bias field winding 220.

The bias field winding 220 may be connected to any suitable source of electrical energy so as to provide an output voltage from the generator 22 in such a direction as to slowly reverse the shear motor H to return the shear to its normal rest position. The main field winding 22b may be supplied with electrical energy from a rectifier circuit 23 comprising a plurality of grid controlled rectifier devices 24TU, 2'5TU and 26TU, which may be connected to a polyphase source represented by conductors 25, through transformers 3 26, 21 and 2B in a manner well known in the art. The conductivity of the rectifier devices may be controlled by means of a regulator represented generally by the numeral 30, so as to normally balance the efiect of the bias field winding 220.

The regulator 35 may, for example, comprise amplifier stages 32 and 33 including valve devices ZBTU and ZITU in the first stage, which may be coupled by means of a coupling transformer 35 to valve devices 22TU and 23TU in the second stage for controlling the voltage applied to the control electrodes 3E, 37, and 38 of the rectifier devices 24TU, 25TU and ZBTU, respectively.

A limiter valve device BTU may be provided for producing a voltage drop in resistors 28R. and 29R when the A.-C. signal voltage across the secondary of the coupling transformer 35 exceeds that across resistor 30R, so as to reduce the signal voltage applied to the second stage 33 of the amplifier. A balance potentiometer P may be provided on the input side of the amplifier stage 32 for adjusting the output voltage of the regulator. It may be adjusted to provide an output voltage under zero input conditions so that the main field winding 2% neutralizes the effects of the bias field winding 220 in the rest position.

In order to provide for starting the shear motor I! in the proper timed relation to a predetermined control condition, such as movement of the strip l9, control means, such as the timer 40, may be provided for supplying a starting impulse for controlling the operation of the regulator 35. The timer 40 may, for example, comprise a circuit such as disclosed in the copending application Serial No. 165,210 of Edward C. Hartwig, having for example, a control valve 4| with its control electrode 42 disposed to be connected to capacitor discharge circuits including capacitors 43 and 44 having valve devices 8TU and BTU associated therewith for controlling their respective discharge circuits. A valve device IGTU may be be provided for controlling the charging of the capacitors in opposite senses from a suitable source such as a battery 45. The valve device BTU and the valve device IGTU may be normally conductive.

Control of the timer 45 may be effected by utilizin scanning devices A and B disposed to be positioned in predetermined spaced relation on the cut-off side of the shear l2 for determining the operation of the capacitor discharge circuits. The scanning devices may each comprise a photoelectric device 49 with an associated source of light 50 arranged so that the strip 19 intercepts the passage of light therebetween. An amplifier 5! in conjunction with the photoelectric device 49 may be disposed to apply a negative control impulse to the control electrode of the valve device IGTU when the leading end of the strip passes the photoelectric device 49 for rendering the valve device non-conductive. The amplifier 5| of scanning device B may likewise be disposed to apply negative and positive control impulses to the valve devices BTU and BTU, respectively, when the leading end of the strip l9 passes its associated photoelectric device.

When the voltages of the capacitors 43 and 4d are substantially equal, the bias on the control electrode 42 of the valve device 4| will be reduced to substantially zero, thus rendering the valve device conductive. This produces a voltage drop across the potentiometer device 19R, in the plate circuit of the valve device and applies a positive timing impulse to the regulator 30 through conductors I65 and I5! for effecting operation of the generator 22 to accelerate the shear motor H. Limit switches i2a, [2b and i2c operatively connected to the shear may be disposed to disconnect the timer from the regulator and the photoelectric amplifiers from the timer after about 200 degrees of shear rotation reclosing at about the 300 degree mark to resetthe system.

In order to control the operation of the shear motor I I, a tachometer generator 53 may be provided for producing a voltage proportional to the speed of the shear motor. This voltage may be applied to the regulator 30 through a potentiometer l [P in opposed relation to the timer voltage so as to provide a speed limiting control.

With the purpose of locating the shear accurately in a normal position of rest, means such as the synchro system 55 may be provided. The synchro system 55 may comprise a synchro device 53 having its rotor 5511 connected in driving relation with the shear I2 and connected for energization from a source of alternating-current represented by one pair of the conductors 25. A reference synchro device 58 may be utilized, having its rotor 58a also energized from the same pair of conductors 25.

The stators 56b and 58b of the two synchro devices may be connected together electrically with resistors 65] disposed in circuit relation therewith. A difference voltage derived from across one of the resistors 55 may be rectified by means of a valve device ZTU and applied to the regulator 30 through a potentiometer device 2P, cumulatively with respect to the timer voltage and in opposition to a fixed reference voltage which may be supplied from a source such as a battery 52, in conjunction with a potentiometer IP. The positional, reference and speed responsive voltages may be applied to the regulator through a sensitivity potentiometer 3P.

In order to stabilize operation of the regulator 35, a voltage may be derived from across the armature 22a of the main generator and applied to the regulator through a capacitor 168 and an antihunt potentiometer 121? so as to produce an effect tending to oppose changes in the output voltage of the generator 22.

With a View to preventing too sudden acceleration or deceleration of the shear motor l1, current limit means 68 may be provided for modi fying the operation of the regulator 35 in con trolling the shear motor H. A voltage may be derived from across a control resistor 58 connected in the armature circuit of the shear motor, and applied to valve devices 3TU and 4TU through a current limit potentiometer 4P. The valve devices 4TU and 3TU may be coupled to a rectifying valve 5TU by means of a coupling transformer H! for modifying the grid voltages of the valve devices 22TU and 23TU of the regulator 30, so as to limit the acceleration and deceleration of the shear motor when the armature current thereof tends to exceed a predetermined safe value.

In operation, the passag of the leading edge of the strip 19 by the photoelectric devices of the scanners A and B produces impulses in spaced time relation in accordance with the speed of the strip. The first of these impulses stops the charging of the capacitors 43 and 44 and hence initiates the timing interval of the capacitor 43, the voltage of which thereupon proceeds to drop in accordance with the well-known exponential characteristic. The second impulse determines the timing period of the capacitor 44, the voltage of which thereupon proceeds to drop accordin to the exponential characteristic, while that of the capacitor 43 remains at a fixed value.

When the voltages of the two capacitors are substantially equal, the valve device M is rendered conductive and a timing impulse corresponding to the curve (a) of Fig. is applied to the r gulator 30 through conductors I55 and 51. This voltage is amplified in two stages by the amplifier tubes ZQTU and ZITU, 22TH and so that a positive grid voltage is applied to the control grids 36, 3? and 33 of the rectifier devices E TU, 25'I'U and ZBTU. Accordingly, the field winding 22b of the main generator 22 w .3 be energized at a maximum value determined by the limiting action of the current limit circuit 6t and the shear motor I! is rapidly accelerated to effect operation of the shear E2 to out the strip [3.

As the shear motor i? accelerates, the voltage of the tachometer generator 53 (curve b of Fig. 3) builds up proportionately, the regulator 30 thereupon acts to hold the speed of the more or less constant. When the shear has rotated about 260, the limit switches E22) and 120 open, disconnecting the timer A l from the regulator and disconnecting the scanning devices A and B from the timer. With removal of the timing voltage, the regulator immediately acts to reduce the voltage of the main gene; and bring the shear motor I? to zero speed under the influence of the differential between the ref" erence and position responsiv voltages. This action proceeds at a rate determined by cur rent limit means.

As the speed of the shear approaches s re, the operation of the synchro system 55 becomes more important. Since the voltage output of the syn chro system varies with the position of the shear, as shown by the curve of 8, it will be realized that the difference between the output voltage of the synchro system and the fixed sierence voltage (curve d of Fig. 3) from the potentiometer 5P will produce a reversible difference voltage which is reduced to a zero value only in the rest position of the shear. In the rest position the regulator is disposed to produce an out put voltage of about l5 volts which is sufficient to neutralize the effects of the generator bias field winding.

Should the shear creep from this rest posit on, a positive voltage will be available for opera the regulator to increase its output voltage to operate the shear in a forward direction to return it to the rest position, or negative blocking volt-- age will be applied to the rectifier devices MTU, ZSTU and 2iiTU While the bias field winding 22c will produce reverse voltage to effect operation of the shear in the reverse direction to return it to the rest position. When the shear is substantial1y returned to the rest position, the limit switches Etc, 12b and 120 will be reclosed to reset the control system for a subsequent cutting operation.

The length of the sheet to be cut from the strip I9 may be determined by moving the scanning devices A, and B as a unit longitudinally with ref erencc to the shear 22. Since the speed of the conveyor belt 28 is greater than that of the strip is, any tendency of the strip !8 to overlap a sheet which has been cut therefrom due to momentarily increased. speed of the strip l9 resulting from the momentary pulse in the sheet i3 straightening out when the shear blades separate, may be compensated for by locating the scanning devices A and B at a sufficient distance from the shear. With a control of this type, it has been found that lengths of less than 5 feet and greater than 18 feet may be cut from strips having speeds varying from 3% to 215 feet minute, with a high degree of accuracy.

From the above description and the accompanying drawings. it will be apparent that I have provided in a simple and inexpensive manner for controlling the operation of a simple e of upcut shear so that it may be used to cut accurate lengths from a strip of moving material over a relatively wide range of strip speeds. The con trol system regulates the position of the shear, controls acceleration of the shear motor, regu lates the top speed of the shear, controls the rate of slowdown, and also automatically the time of shearing to conform with changes in strip speed.

Since certain changes may be above-described construction, bodiments of the invention may be m do without departing from the spirit and scope tit is intended that all the matter contained in the above description and shown in the accompanying drawings shall be considered as illustrative and not in a limiting sense.

I claim as my invention:

1. In combination with a motor connected in driving relation with a shear for cutting predetermined lengths from a moving strip of material, a pair of light sensitive devices disposed to be positioned at different distances from the shear and in predetermined longitudinally spaced relation with each other on the out ard side of shear for producing voltage impulses timed relation with passage of the leading no of the strip, circuit means operable to pounce a control impulse in response to said voltage impulses after a time interval which varies with interval hetween said voltage impulses, a regulator, a circun connecting said circuit means to the regulatoi effect energization of the motor to accelerate tl. shear in response to said control impulse, and switch means operatively connected to the sh r disposed to disconnect the circuit means from the regulator.

2. The combination with a motor connected in driving relation with a shear for cutting a moving length of material, light sensitive means connected to produce impulses spaced in accordance with the speed of the material, a timer having a plurality of timing circuits disposed to be controlled by said impulses to produce im pulse signal in delayed relation with the passage of the material past the light sensitive means, said delayed relation being determined by the interval between the impulses, generating means connected to supply electrical energy to the motor including a regulator responsive to said impulse signal, tachometer means operable to provide a voltage proportional to the speed of the shear, position responsive means operable to produce a voltage variable in accordance with the position of the shear, and circuit means connecting the tachometer means and the position responsive means to the regulator with the timer and position responsive voltages opposing the voltage of the tachometer means, for controlling operation of the generating means.

3. In a control system for a motor connected in driving relation with cutting apparatus, a timer having a plurality of timing circuits connected to produce an initiating impulse, generazna-cle in the different erntor means connected to supply electrical energy to the motor including a regulator connected to be responsive to said impulse, position responsive means operable to produce a voltage variable with the position of the cutting apparatus, circuit means connected to apply the position voltage to the regulator cumulatively with respect to the impulse, and additional circuit means connected to apply a fixed reference voltage to the regulator in opposition to said impulse and position voltages, for controlling the output voltage of the generator means.

4. In a control system for a motor disposed to be connected in driving relation with cutting apparatus for cutting different predetermined lengths from a moving length of material, a timer having circuit means connected to produce a signal impulse in timed relation with the passage of the material past a pair of control stations, generating means connected to supply electrical energy to the motor including a regulator connected to respond to said signal impulse, position responsive means including a synchro device disposed to be connected to the cutting apparatus and a reference synchro device, said synchro devices being connected to produce a difference voltage which varies with the position of the cutting apparatus, and circuit means connected to apply the variable difference voltage to the regulator in opposition to a fixed reference voltage to effect operation of the generating means to return the cutting apparatus to a rest position determined by the balance point of the difference and reference voltages.

5. In a control system for a motor connected in driving relation with cutting apparatus, a timer having a plurality of timing circuits con trolled in timed relation with movement of a material to be cut to provide a control impulse, a regulator responsive to said impulse to supply electrical energy to the motor, and control means responsive to the position of the cutting apparatus operable to apply a position responsive voltage to the regulator to operate the motor to return the cutting apparatus to its initial position.

6. The combination with a motor connected in driving relation with cutting apparatus having a normal rest position, of circuit means connected to provide a voltage impulse in delayed relation with the passage of a strip of material past a control point in accordance with the speed of the strip, a regulator connected to effect operation of the motor in accordance with the impulse from the circuit means, and control means responsive to the operating position of the ,motor operable to apply a position responsive signal to the regulator to effect operation of the motor to return to the rest position.

7. The combination with a motor connected in driving relation with cutting apparatus for cutting a moving length of material, of a circuit means connected to provide a voltage in timed relation with the speed of the material, a regulator disposed to effect energization of the motor to operate the cutting apparatus in response to said timer voltage, tachometer means operable to produce a voltage in opposition to the voltage of said circuit means and proportional to the speed of the cutting apparatus, and position responsive means connected in driving relation with the cutting apparatus to produce a voltage responsive to the position of the shear and in opposition to the tachometer voltage.

8. In a control system for a motor disposed to be connected in driving relation with cutting apparatus, circuit means connected to provide an initiating impulse delayed in a variable timed relation with the passage of a material to be out past a reference point dependent on the rate of passage, generating means connected to supply electrical energy to the motor including an electronic regulator, a circuit connecting said circuit means to the regulator to control the generator in response to said initiating impulse, additional circuit means connected to the regulator to modify the operation in accordance with the speed and position of the motor, and switch means operable to disconnect the first-mentioned circuit means from the regulator when the motor reaches a predetermined operating position.

9. In a control system for a motor, a generator connected to supply electrical energy to the motor, said generator having a plurality of field windings, one of said field windings being connected to a source of electrical energy to effect energization of the motor in a reverse direction, a regulator connected to another of said field windings to eifect energization thereof to effect operation of the motor in a forward direction, a timer having a plurality of timing circuits connected to provide an initiating voltage impulse for effecting operation of the regulator, a tachometer generator disposed to produce a voltage proportional to the speed of the motor, position responsive means disposed to produce a voltage variable with change in position of the motor, circuit means connecting the tachometer generator and the timer with their voltages in additive relation and in opposition to the posiion responsive voltage and a fixed source of reference voltage for controlling the regulator, and switch means operable in response to movement of the motor to disconnect the timer from the regulator after about one-half a revolution of the motor and reconnect it before one revolution is completed.

FRANK VANDENBERG.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,991,083 Dean Feb. 12, 1935 2,195,006 Gullilcsen Mar. 26, 1940 2,298,877 Edwards et a1. Oct. 13, 1942 2,361,466 Fitzsimmons Oct. 31, 1944 FOREIGN PATENTS Number Country Date 581,802 Germany Aug. 3, 1933 

